From Medscape Medical News
Nick Mulcahy
August 13, 2010 — There is "no convincing evidence" that a form of vitamin A, retinyl palmitate, which is an ingredient in many sunscreens, including top-selling brands, is carcinogenic.
This conclusion is made in an analysis authored by dermatologists published online August 6 in the Journal of the American Academy of Dermatology.
Lead author Steven Q. Wang, MD, from Memorial Sloan-Kettering Cancer Center in New York City, said the analysis is a response to the widely publicized 2010 Sunscreen Guide from the Environmental Working Group (EWG), a nonprofit research organization located in Washington, DC.
In their sunscreen guide, which was published in May, the EWG raised concerns about the safety of retinyl palmitate, and at that time the story was covered by many major media outlets, including WebMD.
The EWG said that sunscreen makers have added retinyl palmitate and related forms of vitamin A to 41% of sunscreens on the market in 2010.
The guide advised consumers to avoid sunscreens with retinyl palmitate, and recommended a variety of brands without the ingredient.
We have a disagreement over the data.
The EWG has written that government data "suggest" that retinyl palmitate is carcinogenic on skin exposed to sunlight.
In their analysis, Dr. Wang and colleagues take a look at these government data from the National Toxicology Program (NTP), part of the Department of Health and Human Services.
Unlike the EWG, Dr. Wang and colleagues do not see evidence that is highly suggestive that retinyl palmitate in sunscreen is carcinogenic.
"We have a disagreement over the data," Dr. Wang told Medscape Medical News.
Limiting sun exposure and wearing protective clothing are even more important.
The parties in this debate agree on one thing: sunscreens are not the most important form of protection against the sun. "Limiting sun exposure and wearing protective clothing are even more important for protecting your skin from cancer and premature aging," writes the EWG in their sunscreen guide.
Dr. Wang and his coauthors concur.
They write that "other photoprotection practices, such as avoiding excessive sun exposure, seeking shade, and wearing photoprotective clothing, hats, and sunglasses" should "serve as the primary tactic to reduce skin cancers and minimize photoaging changes associated with UV exposure."
Ten Years and Counting for FDA-NTP Guidance on Retinyl Palmitate
Ten years ago, in 2000, retinyl palmitate was selected for phototoxicity and photocarcinogenicity testing by the NTP, explain Dr. Wang and his coauthors.
The NTP proceeded with the testing on retinyl palmitate but the data are unpublished. Neither the NTP nor the US Food and Drug administration (FDA) has issued a final report on the findings. However, an FDA spokesperson told Medscape Medical News that a draft "technical report" based on these data will be available in mid-December.
Meanwhile, some of these rough data are available on the NTP's Web site; these have been reviewed by both the EWG and Dr. Wang and his colleagues.
Before delving into the NTP data, Dr. Wang and colleagues provide background on retinyl palmitate. They note that it is the storage form of retinol or vitamin A, which is "an essential and endogenous nutrient for human beings."
Human beings already have retinyl palmitate in their skin.
"Human beings already have retinyl palmitate in their skin," simplified Dr. Wang.
They also stress that a review of retinyl palmitate by the NTP is not damning of the compound.
"It should be emphasized that mere selection for testing does not mean the chosen compounds are dangerous or unsafe," the authors write.
"Retinyl palmitate was selected because of its widespread use in cosmetics and sunscreen products," they add.
The FDA's Voluntary Cosmetics Registration Program indicates that the number of formulations containing retinyl palmitate increased from 355 in 1992 to 667 in 2000, the authors point out.
"It is worthy to note that retinyl palmitate has also been used as a food additive and approved for use in over-the-counter and prescription drugs by the FDA," they write.
What the NTP Data Says—2 Versions
The EWG claims that the NTP data indicate that "tumors and lesions developed up to 21% sooner in lab animals coated in a vitamin A–laced cream (at concentrations of 0.1% to 0.5%) than in control animals treated with a vitamin-free cream."
As part of the NTP testing, the animals (lab mice) were exposed to the equivalent of up to 9 minutes of noontime Florida sunlight each day for a year, according to the EWG. The effects were statistically significant for all dose groups tested, they add.
However, Dr. Wang and his colleagues reviewed the data in a different manner, says the EWG, which quickly posted an online critique of the analysis from the dermatologists.
Dr. Wang and colleagues examine "only the absolute number of tumors (neoplasms) in exposed animals," writes the EWG. "They ignore data on the rate at which animals developed tumors and other skin damage."
Dr. Wang defended his team's approach. "This is the conventional way of showing results," he said about listing the number of tumors in the mice.
In their analysis, the authors found that the number of malignant neoplasms in the 2 groups of mice—those coated with a vitamin A–containing cream and those with a vitamin-free cream—exposed to low-dose UV radiation was significantly different. In the mice exposed to higher doses of radiation, the number of malignant neoplasms was not significantly different.
"Therefore, there is no conclusive evidence to indicate that the combination of [retinyl palmitate] and UV is photocarcinogenic," they write.
However, the EWG objected to the conclusion, which they say ignores the results in the mice exposed to low doses of radiation and concentrates on the results in mice exposed to high doses.
"This conclusion disregards the fact that animals in the higher-UV group were massively sickened by the sheer amount of UV radiation (with 82% developing malignant tumors, compared to 38% in the lower-dose group), potentially overwhelming the impact of skin damage caused by vitamin A," the EWG writes.
Dr. Wang believes his team's work was well done and subject to more scrutiny than the EWG's analysis. "The critical difference in our 2 presentations is that ours is in a peer-reviewed journal."
Conflict of Interest Questions
In their analysis, Dr. Wang and his coauthors—Stephen Dusza, DrPH, from Memorial Sloan-Kettering, and Henry Lim, MD, from the Henry Ford Hospital in Detroit, Michigan—report that there were no funding sources for the article. They also declare no conflicts of interest.
The EWG found these article-based disclosures misleading. Elsewhere, the EWG says, Dr. Wang and Dr. Lim have disclosed industry ties.
"Dr. Wang has disclosed that he has been a consultant to La Roche-Posay" the EWG writes in their online critique, saying that the company "markets sunscreens and uses vitamin A in eye creams."
"Dr. Lim has disclosed a consulting relationship with Johnson & Johnson (the maker of vitamin A–containing Neutrogena and Aveeno sunscreens) and La Roche-Posay," the EWG adds.
"Drs. Wang and Lim also volunteer on the Photobiology Committee of the Skin Cancer Foundation, a trade organization supported by the sunscreen industry. This committee sets criteria for the foundation's Seal of Recommendation and reviews the applications of companies [asking] to use the Seal on their products. Each company seeking the Foundation's endorsement must pay an annual $10,000 fee," the EWG further points out.
However, Dr. Wang suggested this was overblown. "We had no conflict of interest for this manuscript—no funding for this commentary," he said.
Furthermore, as part of the publication process at the Journal of the American Academy of Dermatology, the authors were required to fill out forms disclosing involvement with industry, said Dr. Wang. "That's how they found the other disclosures," he said, referring to the EWG. However, the text of article does not reveal where to access those forms.
J Am Acad Dermatol. Published online August 6, 2010. Abstract
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